The invention relates to a method of direct steel making wherein liquid iron is produced in a melter-gasifier system using petroleum coke as the primary reductant for a high grade low silica iron ore and then the hot liquid iron is changed directly into an oxygen blown steel making reactor for steel refining and production.
U.S. Pat. No. 5,259,864 issued from copending U.S. patent application Serial No. 07/958,043 discloses a method for the disposal of an environmentally objectionable material and provision of a new and unexpectedly superior fuel source for processes utilizing melter gasifiers to make molten iron or steel preproducts. Petroleum coke makes an excellent source of carbon in processes for making molten iron or steel preproducts in which a melter gasifier unit is used. Moreover, the reaction in these processes utilizing the petroleum coke as a fuel in the melter gasifier tend to combust the petroleum coke substantially completely with reduction gas as the only gaseous product. Most residual sulfur is carried as a sulfide over with the slag formed in the melter gasifier and can be removed and disposed of or recycled with the slag. Heavy metals are carried over in stable form in solution in the molten iron or steel preproducts and will solidify therewith. A melter gasifier is used in the system and has an upper fuel charging end and a reduction gas discharging end and a lower molten metal and a slag collection end. Entry means are provided into the melter gasifier for charging ferrous material, usually in particulate form, into the melter gasifier. Petroleum coke also in particulate form is introduced into the melter gasifier at the upper fuel charging end. Oxygen-containing gas is blown into the petroleum coke in the melter gasifier to format least a first fluidized bed of coke particles formed by combustion of petroleum coke. Particulate ferrous material is introduced into the melter gasifier through the entry means. Petroleum coke, oxygen and particulate ferrous material are reacted to combust the major portion of the petroleum coke. Reduction gas and molten iron or steel preproducts are produced and a slag is formed which will contain sulfur freed by combustion of the petroleum coke. Heavy metals from the petroleum coke are carried over in stable form and go into solution in the molten iron or steel preproducts. The slag and the sulfur contained therein are removed from the melter gasifier for disposal or recycle.
U.S. Pat. No. 4,849,015 to Fassbinder et al. discloses a method for two-stage melt reduction of iron ore, in which iron ore is prereduced substantially to wustite and at the same time melted down in a melting cyclone, and then liquid hot metal is produced in an iron bath reactor connected to the outlet of the melting cyclone and receiving the melted wustite by adding carbonaceous fuels and oxidizing gas to the melt. The resulting reaction gas from the melt is afterburned, and the dust-laden, partly burned reaction gases from the iron bath reactor are accelerated and further afterburned by adding a hot blast with a temperature of 800.degree. C. to 1500.degree. C., and at least a portion of such accelerated, after burned reaction gases are introduced into the melting cyclone to reduce and melt fresh iron ore. Carbonaceous fuels, such as coke, carbonized lignite, petroleum coke, etc., but preferably coal of varying quality, are fed to the melt in the iron bath reactor. Slag-forming additives, such as lime, fluorspar, etc., are also fed to the iron melt to set the desired slag composition.
U.S. Pat. No. 4,806,158 to Hirsch et al. discloses a process for the production of reduced iron oxide-containing materials. Iron oxide and solid carbonaceous reducing agent are charged into a first expanded fluidized bed, which is supplied with an oxygen-containing fluidizing gas. The gas residence time selected is controlled in the reactor containing the first fluidized bed so that the reduction potential will result in a reduction of the iron oxide material not ill excess of the FeO stage. A gas-solids suspension discharged from the first fluidized bed is supplied to a second expanded fluidized bed, which is supplied with a strongly reducing fluidizing gas. Strongly reducing gas and a major portion of the resulting devolatilized carbonaceous material are discharged from the upper portion of the second fluidized bed. Reduced material having a metallization of 50 to 80% and the remaining devolatilized carbonaceous material are discharged from the lower portion of the second fluidized bed. Suitable carbonaceous materials include all coals, from anthracite to lignite, carbonaceous minerals and waste products, such as oil shale, petroleum coke or washery refuse, provided that they are solid at room temperature. The oxygen-containing gas preferably consists of oxygen or of oxygen-enriched air.
U.S. Pat. No. 4,897,179 to Mori et al. provides a method of producing reduced iron and light oil from iron ore and heavy oil which comprises a thermal cracking step of subjecting heavy oil to thermal cracking while retaining iron ore particles in a fluidized state to produce light oil and simultaneously to deposit coke as by-product on the surface of the iron ore particles; a gasification step of putting the coke-deposited ore in contact with an oxidizing gas including steam and oxygen in a fluidized state to react the coke with the gas thereby to produce a reducing gas containing hydrogen and carbon monoxide and of heating the coke-deposited ore upward of a reduction temperature of iron ore by partial oxidization of the coke; and a reduction step of reducing the coke-deposited iron ore in a fluidized state by the reducing gas to produce reduced iron. When the gasification step is performed by an oxidizing gas containing a majority of steam and up to 15 vol. %, based on the steam, of oxygen at 800.degree.-1000.degree. C. under a pressure of 0-10 kg/cm.sup.2 G, a reducing gas containing high-concentration hydrogen gas is obtained.
Slags of high sulfur capacity have been utilized in applications associated with ferrous metallurgy. Kleimeyer et al. in U.S. Pat. No. 4,600,434 describe the use of high sulfur capacity slag and magnesium metal to desulfurize molten iron while it is contained in a torpedo car. Quigley, U.S. Pat. No. 4,853,034, describes using a vanadium-bearing, high-magnesia synthetic calcium aluminate slag for absorbing sulfur during ladle refining of steel. Knauss et al., U.S. Pat. No. 4,695,318, describe using a synthetic slag similar to that of U.S. Pat. No. 4,853,034, and the refractory brick of the ladle itself, to desulfurize molten iron contained in said ladle.
In recent years methods utilizing a melter gasifier have been developed to produce molten iron or steel preproducts and reduction gas. Most of these processes utilize a coal, fluidized-bed. A high temperature is produced in the melter gasifier utilizing coal and blown in oxygen to produce a fluidized bed and iron sponge particles are added from above to react in the bed to produce the molten iron.
A melter gasifier is an advantageous method for producing molten iron or steel preproducts and reduction gas as described in U.S. Pat. No. 4,588,437. Thus there is disclosed a method and a melter gasifier for producing molten iron or steel preproducts and reduction gas. A first fluidized-bed zone is formed by coke particles, with a heavy motion of the particles, above a first blow-in plane by the addition of coal and by blowing in oven-containing gas. Iron sponge particles and/or pre-reduced iron ore particles with a substantial portion of particle sizes of more than 3 mm are added to the first fluidized-bed zone from above. A melter gasifier for carrying out the method is formed by a refractorily lined vessel having openings for the addition of coal and ferrous material, openings for the emergence of the reduction gases produced, and openings for tapping the metal melt and the slag. Pipes or nozzles for injection of gases including oxygen enter into the melter gasifier above the slag level at least two different heights.
Another process utilizing a melter gasifier is described in U.S. Pat. No. 4,725,308. Thus there is disclosed a process for the production of molten iron or of steel preproducts from particulate ferrous material as well as for the production of reduction gas in the melter gasifier. A fluidized-bed zone is formed by coke particles upon the addition of coal and by blowing in oxygen-containing gas by nozzle pipes penetrating the wall of the melter gasifier. The ferrous material to be reduced is introduced into the fluidized bed. In order to be able to produce molten iron and liquid steel preproducts in a direct reduction process with a lower sulfur content, the ferrous material to be reduced is supplied closely above the blow-in gas nozzle plane producing the fluidized bed. An arrangement for carrying out the process includes a melter gasifier in which charging pipes penetrating its wall are provided in the region of the fluidized-bed zone closely above the plane formed by the nozzle pipes. The ferrous material to be melted as well as the dusts separated from the reduction gas and, if desired, fluxes containing calcium oxide, magnesium oxide, calcium carbonate and/or magnesium carbonate are introduced therethrough.
U.S. Pat. No. 4,793,855 to Rolf Hauk discloses process for the gasification of sewage sludge or other carbon-containing waste materials in a gasifier. A solid fuel and oxygen-containing gas are also fed into the gasifier. The solid fuel may be coal or petroleum coke. The residues formed during gasification collect at the bottom of the gasifier in the form of molten slag. Gasification takes place in a fluidized bed formed above the slag bath and constituted by the dried sewage sludge or waste materials, the solid fuel, the oxygen-containing gas and the gasification gas. The gas produced in the gasifier can be used for power generation or as a reducing gas for iron ore. Sponge iron can simultaneously be melted in the gasifier and reduced to pig iron.
There is also a process that utilizes a combined reduction furnace and melter gasifier known as the COREX.RTM. process (COREX.RTM. is a trademark of Deutsche Voest-Alpine Industrieanlagenbau GMBH and Voest-Alpine Industrieanlagenbau). This process is described in Skilling's Mining Review, Jan. 14, 1989 on pages 20-27. In the COREX.RTM. process the metallurgical work is carried out in two process reactors: the reduction furnace and the melter gasifier. Using non-coking coals and iron bearing materials such as lump ore, pellets or sinter, hot metal is produced with blast furnace quality. Passing through a pressure lock system, coal enters the dome of the melter gasifier where destructive distillation of the coal takes place at temperatures in the range of 1,100.degree.-1,150.degree. C. Oxygen blown into the melter gasifier produces a coke bed from the introduced coal and results in a reduction gas consisting of 95% CO+H.sub.2 and approximately 2% CO.sub.2. This gas exits the melter gasifier and is dedusted and cooled to the desired reduction temperature between 800.degree. and 850.degree. C. The gas is then used to reduce lump ores, pellets or sinter in the reduction furnace to sponge iron having an average degree of metalization above 90%. The sponge iron is extracted from the reduction furnace using a specially designed screw conveyor and drops into the melter gasifier where it melts to the hot metal. As in the blast furnace, limestone adjusts the basicity of the slag to ensure sulfur removal from the hot metal. Depending on the iron ores used, SiO.sub.2 may also be charged into the system to adjust the chemical composition and viscosity of the slag. Tapping procedure and temperature as well as the hot metal composition are otherwise substantially the same as in a blast furnace. The top gas of the reduction furnace has a net calorific value of about 7,000 to 8,000 KJ/Nm.sup.3 and can be used for a wide variety of purposes.
The fuels used in these processes are typically described as a wide variety of coals and are not limited to a small range of coking coal. The above-noted article from Skilling'S Mining Review notes that petroleum coke suits the requirements of the COREX.RTM. process. Brown coal and steam coal which are relatively poor quality coal having a relatively high ash content. i.e. plus 15%, have been identified as suitable for use in these processes. Coke made from coal has also been identified as a fuel for many of the processes utilizing melter gasifiers.
U.S. Pat. No. 4,946,498 to Ralph Weber shows a steel making vessel of an energy optimising furnace ("EOF") which is also described in the journal MBM-Metal Bulletin Monthly, October 1986, on pages 47 to 51, and is used for melting the iron sponge particles and into which oxygen is injected. Arranged above the melting vessel is a charging material preheater. The melting vessel accommodates a molten iron bath. Beneath the surface of the molten iron bath, under-bath nozzles open into the melting vessel for the injection of oxygen and possibly solid materials such as pulverized coal or additives, by means of a carrier gas. Above the level of the bath, further nozzles open into the melting vessel for the injection of oxygen or pre-heated air which can be supplied by way of a ring conduit and which serves for post-combustion of the CO-bearing waste gas which rises out of the molten bath. The installation also has oil-oxygen burners. The melting vessel can also be supplied with scrap which as been pre-heated by the hot waste gases from the melting vessel, in a scrap preheater which is fitted onto the melting vessel.
This application is related to U.S. patent application Ser. No. 07/958,043 filed Oct. 6, 1992, now U.S. Pat. No. 5,259,864; U.S. patent application Ser. No. 07/991,914, filed Dec. 17, 1992, U.S. patent application Ser. No. 08/056,341, filed Apr. 30, 1993 and U.S. patent application Ser. No. 08/084,888 filed Jun. 30, 1993. The disclosures of these applications are incorporated herein for all purposes.